Valve seat cutter



Ap 1936- B. F. -STOWELL in AL 2,036,555

VALVE SEAT CUTTER Filed June 8, 1932 INVENTORS A" gym! ESTdIp/ELL YATTORNEYS Patented Apr. 7, 1936 UNITED STATES PATENT OFFICE VALVE SEATCUTTER. Byron F. Stowell and Roger 8. Pym, Springfield,

Mass assignors to Van Norman Machine Tool Company, Springfield, Mara, acorporation of Massachusetts Application June s, 1932, Serial No.015,912 1 Claim. (01. 29-10:)

a cutter at a marketable price, to lower the grade of steel below whatwould be theoretically desirable. Attempts have also been made to securethe advantages of high grade steel without a prohibitive cost by usingcutters of the inserted blade type. The forms of inserted blade cuttersheretofore proposed for this purpose have not been entirelysatisfactory, and it is the" general object of the present invention toimprove upon them in several particulars.

One object of the invention is to produce a cutter which will hold itscutting edge without resharpening for a longer time than was possiblewith prior cutters. A further object is to provide a superior cutter ata lower manufacturing cost. A further object is to produce a cutterwhich will be free from chatter during operation. A further object is toprovide an'inserted blade cutter which may be used upon a tapered pilotor arbor. A further object is to provide a cutter which will leave amore perfect finish on the valve seat than has heretofore been possible.Additional objects will appear from the following description andReferring to the drawing:

Fig. 1 is a perspective view of a valve seat cutter embodying ourinvention;

Fig. 2 is a bottom view thereof;

Fig. 3 is a section on line 3-3 of Fig. 2;

Fig.4 is a side elevation of a central bushing forming a part of thecompleted cutter;

Fig. 5 is a top plan view of the bushing shown in Fig. 4;

Fig. 6 is a detail, on an enlarged scale, of one form of cutting blade;

Fig. '1 is a view of the blade shown in Fig. 6, looking from the left inthat figure; I

I ig.8isaviewsimilarto1 'ig.6showlngadifferent form of cutting blade;

Fig. 9 is a'similar view showing a still different form of blade; andFig. 10 is-a view similar to Fig. 3. showing a modified form of cutter.

The cutter comprises a body portion I l preferably of a hard zinc alloy,and bears series of blades II, II, and it, formed of high grade steeland permanently united to the base at the time the latter is cast. Thecenter of the cutter is preferably formed by a bushing ll made of a hardmaterial such as steel, having its outer surface formed withcircumferential grooves I! and peripheral knurlings or fiutings I. Thisbushing is also permanently united to the body II at the time the latteris cast, the fiutings and 10 grooves preventing any possibility of shiftafter the material of the base has hardened. The interlor ll of thesleeve is preferably tapered so that the cutter may be mounted withoutfurther interconnection upon a tapered arbor or pilot of 1 the usualtype. If desired, however, the bushing ll may be omitted and theinterior of the central hole in the cutter left cylindrical as in Fig.10. In this case the body of the cutter is formed with lug engagingportions it or similar devices by which the cutter may be rotated by anarbor or pilot having suitable lugs or dogs thereon.

The blades are, as stated above, preferably of three kinds in order tosecure the advantages present in one aspect of the invention. Each kindis made of a'high grade tool steel, preferably of a tungsten alloy, andis heat treated so as to render it suitable for cutting. The specialmanner of heat treatment will depend upon the particular alloy used, as.is'well understood in the art. Each blade is provided with some meansfor causing it to become permanently located in the cast base when thelatter has become solidified, so that the blades will not become looseunder the strains of use. shown the means chosen comprises a series offlutings or depressions i9 adjacent what is to become the inner edge ofthe blade, the fiutings being indented from opposite sides of the bladeIn the embodiment and preferably tapering from a point 2| to the innerblade edge. By reason of this tapering and the raised character of thefiutings when considered in relation to the general plane of the side ofthe blade, the blades will be anchored firmly in place against a forcetending to dislodge them in any direction when the matrix of castmaterial in which they are set has hardened.

Each of the blade types may, if desired, be beveled as at 2| on onecorner, so that when the blades are mounted in the body these beveledally similar to each other, having notches I! cut in their edges. ."Thenotches are preierablydiiierently positioned in the two cases, however,so that they will out of line when assembled in the cutter. The bladesl2 and II are preferably alternated around the cutter, as shown in Fig.2;; the notches breaking step as is customary, in nicked tooth cuttersso that the two setsof blades taken together cover the entire surface ofthe valve seat being worked on. Que or more plain blades II areinterposed between adiacent nicked blades, as is also shown in Fig. 2;resulting in a very smooth finish being givento the valve seat whileretaining the added speed of out due to the nicking ofthe teeth. It willbe observed from Fig Z that adjacent blades are unevenly spaced aroundthe base i0. Preferably this unevenness of spacing is such that no bladeis opposite any other blade and no two blades are spaced. similarly.This can be worked out in many ways, depending on the number of bladesused. Using twelve blades, a suitable angular spacing of the blades is27%;, 33, 34, 27, 23 375?, 31%, 34%2 23 38, The angles are measuredbetween adjacent blades, which converge towards the axis of the cutter,and are given consecutively around the cutter. It desired, the plainblades maybe used instead of notched blades, as it has been found that aoutfar of this type with plain blades cuts valve seat scalesatisfactorily. The use of notched blades does, however, add somewhat tothe speed oi. cutting.

Gne relation between the steel blades and the alloy base is ofimportance in making possible the production 01' this type of cutter. Asis known in the heat treatment of alloy steels, the metal when oncehardened and then drawn to a predetermined temperature can subsequentlybe reheated to a lower temperature without destroying the propertiesgiven to it by its heat treatment. The casting temperature of the alloychosen is lower than the drawing temperature aosaeoa of the steel by anamount sumcient to prevent any accidental impairment oi the hardnessgoi'the blades. It will thus be seen that blades can be hardened andsuitably: tempered, subsequently placed in a mold or die, and the moltenalloy for the base poured in place without injuring the blades.

One type of alloy which is suitable for the body II is a standard oneused in die casting and having 88% fzinc, 4% aluminum, 3% copper, and 5%magnesium. This alloy, which is given as illustrative only, hasa'melting'point of 750 degrees and? a pouring temperature in theneighborhood of 380 degrees. contrasted withf this is the tempering heatof a timsten steel aJoy blade of 1056 degrees. It is obvious that iimetals of substantially these characteristics are used, the alreadytempered steel blades may be cast in place without danger of injuringthem.

What we claim is:

An inserted blade cutter comprising a relatively soft body of castmetal, a relatively'fhard metal sleeve centrally located in the body andshaped externally to provide a anchorage with the body, said sleevebeing iormed with a central bore whereby the cutter may be detachablysupported on an arbor, and a plurality of tempered sheet metal bladesset into the body and having their extreme inner edges laterallydistorted with corrugations diminishing in size a they extend into thebodies oi the blades, whereby the extreme inner edge of each blade is ofsubstantially greater thicniess than the body of the blade, and abonding anchorage is provided with the cast metal body, the metal ofwhich the body is formed being of such a composition that its mouldingtemperature is substantially below that at which the blades aretempered.

BYRON 1". S'I'OWEIL.

ROGER S. PYNE.

